The present invention relates to a method and/or system for reducing the concentration of organic fluorides present in a hydrocarbon mixture. More particularly, the invention relates to a method and/or system for reducing the concentration of organic fluorides present in an alkylation reactor effluent.
The use of catalytic alkylation processes to produce branched hydrocarbons having properties that are suitable for use as gasoline blending components is well known in the art. Generally, the alkylation of olefins by saturated hydrocarbons, such as isoparaffins, is accomplished by contacting the reactants with an acid catalyst to form a reaction mixture, settling the mixture to separate the catalyst from the hydrocarbons and further separating the alkylation reactor effluent, for example, by fractionation, to recover the separate product streams. Normally, the alkylation reactor effluent of the alkylation process contains hydrocarbons having five to ten carbon atoms per molecule, preferably seven to nine carbons atoms per molecule. In order to have the highest quality gasoline blending stock, it is preferred for the alkylate hydrocarbons formed in the alkylation process to be highly branched and contain seven to nine carbon atoms per molecule.
Recent efforts to improve conventional hydrogen fluoride catalyzed alkylation processes have resulted in the development of new catalyst compositions that contain hydrogen fluoride and a volatility reducing additive. These new catalyst compositions have been found to be quite effective as an alkylation catalyst and to provide many other favorable benefits. However, it has also been found that in the alkylation process that uses the catalyst mixture containing hydrogen fluoride and such additive there is an increase in the production of undesirable organic fluorides. In fact, as the concentration of hydrogen fluoride in the new catalyst composition becomes more dilute, the amount of organic fluorides produced in the alkylation process increases. Organic fluorides produced can include, but are not limited to, organic fluorides having in the range of from about 3 to about 14 carbon atoms per molecule. Typical organic fluorides produced can include, but are not limited to, 2-fluoropropane, 2-fluorobutane, 2-fluoro-2-methylpropane, 2-fluoropentane, 2-fluoro-2-methylbutane, 2-fluoro-3-methylbutane, methylfluorobutane isomers, 2-fluorohexane, 3-fluorohexane, methylfluoropentanes, dimethylfluorobutanes, fluoroheptanes, fluoromethylhexanes, dimethylfluoropentanes, fluorooctanes, fluoromethylheptanes, dimethylfluorohexanes, fluorotrimethylpentanes fluorononanes, fluoromethyloctanes, dimethylfluoroheptanes, fluorotrimethylhexanes.
In many instances, it is not desirable for the product streams to have an excessively high concentration of organic fluorides.
Therefore, development of an efficient process for reducing the level of organic fluorides present in a hydrocarbon mixture would be a significant contribution to the art.
It is, thus, an object of the present invention to provide an improved process for reducing the level of at least one organic fluoride in a hydrocarbon mixture which is economical and efficient.
A further object of the present invention is to provide an improved system to be used in reducing the level of at least one organic fluoride in a hydrocarbon mixture which is economical in construction and reliable and efficient in operation.
A yet further object of the present invention is to provide an improved system to be used in reducing the level of at least one organic fluoride in a hydrocarbon mixture which includes means for controlling the level of at least one organic fluoride present in the hydrocarbon mixture and/or for controlling the research octane of the hydrocarbon mixture.
According to a first embodiment of the present invention, a method for decreasing the level of at least one organic fluoride present in a hydrocarbon mixture is provided. The method of the first embodiment comprises the steps of:
passing the hydrocarbon mixture to an eductor;
educting into the hydrocarbon mixture a catalyst comprising a volatility reducing additive and hydrofluoric acid to thereby form a hydrocarbon-catalyst mixture;
permitting the hydrocarbon-catalyst mixture to undergo a phase separation to thereby produce a hydrocarbon phase having a lower concentration of at least one organic fluoride than the hydrocarbon mixture and to thereby produce a catalyst phase;
withdrawing at least a portion of the catalyst phase for use as the catalyst; and
withdrawing at least a portion of the hydrocarbon phase to form a hydrocarbon product stream.
According to a second embodiment of the present invention, a process for alkylating at least a portion of a hydrocarbon feedstock comprising olefins and isoparaffins is provided. The process of the second embodiment comprises the steps of:
introducing the hydrocarbon feedstock into an alkylation reaction zone;
contacting the hydrocarbon feedstock with a first catalyst comprising a volatility reducing additive and hydrofluoric acid in the alkylation reaction zone to thereby produce alkylation of at least a portion of the olefins and isoparaffins in the form of an alkylation reaction effluent;
passing the thus-produced alkylation reaction effluent from the alkylation reaction zone to a first settling zone and permitting a phase separation to occur so as to produce a first catalyst phase and to produce a first hydrocarbon phase having a concentration of at least one organic fluoride in the range of from about 150 ppmw to about 10,000 ppmw, based on the total weight of the first hydrocarbon phase, and having a research octane in the range of from about 85 to about 98; and
contacting at least a portion of the first hydrocarbon phase with a second catalyst comprising a volatility reducing additive and hydrofluoric acid to thereby produce a hydrocarbon product stream having a lower concentration of at least one organic fluoride than the first hydrocarbon phase.
According to a third embodiment of the present invention, a system or apparatus is provided comprising:
an alkylation reactor;
a first settler, having an upper portion, an intermediate portion and a lower portion;
an eductor;
a second settler, having an upper portion, an intermediate portion and a lower portion;
first conduit means operably related to the alkylation reactor for introducing a hydrocarbon feedstock comprising olefins and isoparaffins into the alkylation reactor;
second conduit means operably related to the alkylation reactor for introducing a first catalyst comprising a volatility reducing additive and hydrofluoric acid into the alkylation reactor;
third conduit means operably related to the alkylation reactor and operably related to the first settler for withdrawing an alkylation reaction effluent from the alkylation reactor and for introducing the alkylation reaction effluent into the intermediate portion of the first settler, the upper portion of the first settler being operable for containing a first hydrocarbon phase separated from the alkylation reaction effluent and the lower portion of the first settler being operable for containing a first catalyst phase separated from the alkylation reaction effluent;
fourth conduit means operably related to the first settler and operably related to the eductor for withdrawing at least a portion of the first hydrocarbon phase from the upper portion of the first settler and for introducing the at least a portion of the first hydrocarbon phase into the eductor;
fifth conduit means, operably related to the second settler and operably related to the eductor for withdrawing at least a portion of a second catalyst phase comprising a volatility reducing additive and hydrofluoric acid from the lower portion of the second settler and for introducing the at least a portion of the second catalyst phase into the eductor for mixing with the at least a portion of the first hydrocarbon phase to thereby produce a hydrocarbon-catalyst mixture;
sixth conduit means operably related to the eductor and operably related to the second settler for withdrawing the hydrocarbon-catalyst mixture from the eductor and for introducing the hydrocarbon-catalyst mixture into the intermediate portion of the second settler, the upper portion of the second settler being operable for containing a second hydrocarbon phase separated from the hydrocarbon-catalyst mixture and the lower portion of the second settler being operable for containing the second catalyst phase separated from the hydrocarbon-catalyst mixture; and
seventh conduit means operably related to the second settler for withdrawing at least a portion of the second hydrocarbon phase from the second settler to thereby form a hydrocarbon product stream.
Other objects and advantages will become apparent from the detailed description and the appended claims.